The field of histology has been around for so long that the number of “experts” in the field is too great to count. I’m sure one of the early large debates was, how to remove the water in tissue samples. Water is not a good liquid to have on or in any tissues unless they are being stained. After fixation, the tissue is dehydrated in a graded chemical strengths until it is concentrated enough to remove all the water. In clinical settings where speed is necessary, the dehydration has been taken over by automatic tissue processors using 70%, 80%, 95% and 100% ethanol solutions. In the research setting where scientists are more worried about the results of their unknown tissues, hand processing may be implemented. It is in the research setting that unknown conditions play a role in deciding what kinds of dehydrants to use. This is sometimes also dependant on availability of each chemical. If you wanted to look at the pro’s and con’s of different dehydrants but did not have the background or resources to find definitive answers, maybe it would have to be a trial and error situation. That is if there is enough funds to give all the different chemical choices.
We try to help by putting up protocols, procedures, tables and general information as silent aides if you cannot contact us directly.
Two examples of this; if someone was thinking about using the following dehydrants:
Ethlylene glycol monoethyl (Cellosolve). This has a boiling point of 156.4° C and is good for 1. Rapid dehydrant, 2. tissue may stay in it for months without injury, and 3. avoids distortion and does not need graded dilutions. The downside is it is 1. expensive, 2. rapidly absorbs water from the air, and 3. requires a clearing agent.
Tetrahydrofuran with a boiling point of 65° C is 1. miscible in all proportions with water, ether, chloroform, acetone, and the hydrocarbons xylene, toluene, and benzene. 2. Rapid without excessive shrinkage and hardening. 3. Low toxicity; low fire and explosion hazard. 4. Not toxic, 5. has better results than most universal solvents and is a 6. solvents of many mounting medias. However it is 1. odorous- should be used in well-ventilated room and 2. evaporates rapidly. 3. The dyes are not soluble in tetrahydrofuran.
There are many other possible dehydrants that could be used in place of the traditional ethanol that might give better results depending on type of tissues and desired results. For us to talk about all of them, I’m afraid would bore most people. Instead we have created a table posted on this site at:
Hans B Snyder
60 Prescott Street
Worcester, MA 01605